In the art of metal finishing, a major problem exists in connection with large workpieces having a considerable number of different surfaces of revolution (both internal and external) that need to be finished. The conventional method of grinding these workpieces usually requires several set-ups on one or more grinding machines. Following each set-up the finishing of a given surface is carried out on each workpiece in the production lot. Upon completion, the grinding machine has to be reset to execute the next operation and all the workpieces have to be reloaded on the machine to finish another surface. Therefore, considerable time and cost can be saved if a number of operations can be performed for one staging of the workpiece. For that reason, it is desirable to grind a large number of these surfaces simultaneously and, for that purpose, an abrasive wheel that is capable of grinding more than one surface at the same time may be used. This is accomplished by using a formed wheel to grind several surfaces at one time. Unfortunately, in this type of arrangement, it is difficult to to maintain the necessary size and profile accuracy. For instance, it is currently necessary, as the final size is approached, to stop the machine to measure the size of the surfaces manually and to input into the control revised positions for terminating the grind cycle to achieve the correct size. This is complicated by the fact that several surfaces are being finished at the same time. The major source of difficulties with sizing (aside from the fact that it is impossible to provide in-process gaging on such machines) is the fact that a plurality of surfaces of large radius are involved. The fact that two wheelheads for internal and external surfaces must be provided on the large structure of the machine and widely separated (necessitated by the large diameter of the surfaces being finished) means that thermal errors are much larger than would otherwise be true. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a grinding machine for accurately grinding a multiplicity of surfaces simultaneously on a large workpiece.
Another object of this invention is the provision of a grinding machine for finishing a plurality of surfaces of revolution on a workpiece without in-process gaging and without attention from a human operator.
A further object of the present invention is the provision of a grinding machine having a reference plate with contact surfaces, which reference plate is maintained at a constant temperature to permit sizing stability.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.